Commonly, as shown in FIGS. 19 and 20, such a stacking connector 1 has a receptacle connector 3 affixed to a printed circuit board 2, and plug connector 5 affixed to another printed circuit board 4, and by engaging these, the connector simultaneously conducts the positioning of printed circuit boards 2 and 4 and the electrical connection of the wiring on printed circuit boards 2 and 4.
That is to say, receptacle connector 3 is provided with a plurality of contacts 6 which are connected to the wiring of one printed circuit board 2, and a receptacle housing 7 which is in the shape of a box with a floor having a rectangular shape in horizontal cross section, which accepts these contacts 6; plug connector 5 is provided with a plurality of contacts 8 which connect with the wiring of the other printed circuit board 4, and a plug housing 9 which has the shape of a rectangular parallelopiped block and holds the contacts 8 in a unitary manner.
That is to say, when a receptacle connector 3 and plug connector 5 having such a structure are connected, the plug housing 9 is inserted within the receptacle housing 7, and thereby the two are engaged with a gap having a constant fit therebetween, and the printed circuit boards 2 and 4 are positioned with respect to one another with an accuracy depending on the dimensions of the fitted gap.
Now that portable electronic apparatuses such as portable phones and the like have come to be widely used as a result of developments in the miniaturization and reduction in weight of electronic products, in concert with a miniaturization and decrease in weight in the printed circuit boards 2 and 4 installed within such electronic apparatuses, it is also necessary to reduce the size and weight of the connectors 1 connecting these printed circuit boards 2 and 4. In order to reduce the size and weight of such connectors 1, light weight materials are employed, and a reduction in size of contacts 6 and 8 requires that the walls of housings 7 and 9, and in particular, receptacle housing 7, be made thinner, while maintaining the minimum strength required for the positioning and affixing of printed circuit boards 2 and 4.
However, as a result of the reduction in size and weight, there are problems in that the strength of the receptacle housing 7 with respect to impact is reduced when the walls thereof are made thinner. In particular, in portable electronic apparatuses such as portable telephones and the like, there is a high frequency of such impacts during use as a result of droppage and the like, and the receptacle housing 7 may break as a result of the repetition of such impacts.
In particular, as shown by arrow A in FIG. 20, when an impact force is applied in the longitudinal direction to the receptacle housing 7, cracks C are likely to be produced between the side walls 7a and opening end 7b of the receptacle housing 7 disposed at the ends in the longitudinal direction. The reason for this is that the side walls 7c of the receptacle housing 7 which run in the longitudinal direction receive the impact force from the plug housing over a broad surface area, and in addition the points of contact between connectors 6 and 8 are commonly provided in the transverse direction of receptacle housing 7, so that this has the effect of ameliorating the impact force as a result of the elastic deformation of contacts 6 and 8, while the side walls 7a of the receptacle housing 7 disposed at the ends in the longitudinal direction do not have such an amelioration effect, and directly receive the impact force over a narrow surface area.
Furthermore, the reason that cracks C are produced in the corner part between the side walls 7a and the opening end 7b of the receptacle housing 7 is that, because the rigidity of the thin side walls 7a is low, the tensile force operating within the receptacle housing 7 as a result of the impact force is excessive.
In order to avoid such problems, attempts have been made to increase the thickness of the side walls 7a at both longitudinal ends of the receptacle housing 7, and to adopt a rounded shape in order to avoid the concentration of stress at the corner part of side walls 7a of receptacle housing 7; however, in all these cases, receptacle housing 7 has been too large, and this is not desirable.
On the other hand, in the example shown in FIG. 21, stacking connector 10 is disposed between two printed circuit boards 11 and 13, and comprises a plug connector 12, in which a plurality of socket contacts 17 which connect to a plurality of wirings (not depicted in the figure) provided in printed circuit board 11, are housed within a plug housing 15, and a receptacle connector 14, in which a plurality of pin contacts 18, which are connected with a plurality of wirings (not depicted in the figure) provided on the other printed circuit board 13, are housed within a receptacle housing 15. There are many cases in which the stacking height of printed circuit boards 11 and 13 is determined by the height of the electronic parts or the like which are installed on printed circuit boards 11 and 13 are installed. That is to say, as the height of the part which installed on printed circuit board 11 is installed increases, it is necessary to increase the stacking height in order to avoid interference between this part and the other printed circuit board 13, or with electronic parts or the like which are installed on the other printed circuit board 13.
In this case, it is necessary to increase the height of connector 10 in accordance with the stacking height of printed circuit boards 11 and 13; however, conventionally, as shown for example in FIG. 21, this need was met by increasing the height of housing 16 and increasing the length of the contacts 18 within housing 16.
However, when the length of contacts 18 was increased, as shown in FIG. 21, because there was a lengthening of the region in which neighboring contacts 18 were disposed in opposition to one another, there were problems in that the floating capacity generated between contacts 18 was large, and signals transmitted through one contact 18 were induced into another contact 18, so that the so-called cross-talk noise was large.
In particular, in concert with the advances in digital technology in recent years, as a result of an increase in the clock frequency of IC parts and the like, the effects of cross-talk noise have become striking in the state in which signal transmission is accomplished at high speeds.
The characteristics of the floating capacity which is the source of this cross-talk noise are such that the floating capacity becomes larger as the opposed surface areas of the neighboring contact 18 increase, and becomes larger as the gap between the contact 18 becomes smaller.
Accordingly, a widening of the gap between contacts 18, or alternatively, placing electronic shielding between contacts 18, have been considered as methods for reducing such cross-talk noise. However, when the gap between contacts 18 is widened, the dimensions of connector 10 are increased, and furthermore, when electronic shielding is placed between contacts 18, the structure of connector 10 becomes more complex, so that product cost increases.
Furthermore, a reduction in size of the opposed surface areas of the neighboring contacts 18 is also effective as a method of reducing the floating capacity; however, there is a limit to the reduction in thickness of contacts 18 which may be achieved both from the point of view of manufacturing technology and structural strength. For example, in the case of contacts 18 having an overall length of 15 mm, the thickness thereof has a lower limit within a range of 0.1 mm-0.15 mm.